Metrohm tiamo 1.3 Manual - Manual (Page 445)

Commands 419
KFT
Command for volumetric Karl Fischer Titrations ( KFT ).
Principle
With this command volumetric titration for determining the water content by the
Karl Fischer method with automatic pre- and post-conditioning are carried out. A
typical feature of the Karl Fischer titration is the controlled reagent addition, which
depends on the control difference (current measured value – endpoint), with the
aim of reaching the measured value given as being the predefined target endpoint
as quickly and accurately as possible. Overtitrating is avoided to a great extent.
The titration termination at the endpoint takes place either drift-controlled or after a
waiting period. The volume added up to the endpoint gives the calculable reagent
consumption
Reagent addition takes place in three phases during the titration:
• Initial addition
During this phase the dosing rate increases continuously. It starts with the
Min. rate and increases to the Max. rate .
• Continuous addition
Addition is carried out at the
Max. rate until the Control range is reached.
• Control range
In this range addition is finely controlled. Shortly before the endpoint is
reached addition is only carried out at the
Min. rate .